1. Field of the Invention
This invention relates to a process for treating a sludge or a drainage containing chromium (VI) compounds with a solidifying agent. More particularly, it relates to solidify the sludge or the drainage with a calcium haloaluminate bearing rapid hardening cement in a short period of time.
2. Description of the Prior Art:
Chromium (VI) compounds are contained in amounts of more than several ppm as Cr.sup.6+ in a sludge after recovery of chromium from chromium ore or in a drainage discharged from a chromium plating factory, a tanned leather factory and the like and therefore the dumping of the sludge and the drainage causes an environmental pollution. Although these may be solidified by employing portland cements such as normal portland cement, high early-strength portland and portland mixed cements such as fly-ash cement, blast-furnace slag cement and silica cement, it is necessary to reduce Cr.sup.6+ to Cr.sup.3+ in order to produce solidified materials of greater strength by the use of the above-mentioned cements.